Why this claim is harder than it sounds
Competition itself is lawful, and businesses lure customers away from each other every day. When no binding contract existed, New York courts generally require more than hard competition: the conduct usually has to involve wrongful means, such as misrepresentation or another independent wrong, or be aimed solely at harming you. The claim also tends to require a specific relationship with an identifiable third party, rather than a general loss of business. Many other states use similar ideas under different labels, and some are somewhat broader. Interference with an existing contract is a separate claim with its own standards, and it is often easier to plead when a contract was in force.
Building the evidence
These cases depend on showing what the third party was about to do and why it changed course. Proposals, draft orders, emails about renewal, and a history of repeat business can show that a relationship was real and likely to continue. Statements the other side made to your customers or partners, if you can obtain them lawfully, often reveal the means used. Be careful about how you gather that information, since pressuring a former customer or recording conversations in ways the law does not allow can create new problems. Keep records of lost revenue tied to specific accounts, because a general decline is hard to attribute to one competitor. Former employees who took information or customers may raise trade secret or contract claims worth considering together.
Weighing whether to sue
Interference claims are often paired with other claims, such as defamation, unfair competition, or breach of a restrictive covenant, and the stronger case is sometimes one of those rather than interference itself. If you are the one accused, the same high bar is part of the defense, and claims that describe nothing more than competition are often challenged at the pleading stage. When we first meet, we look at the specific relationship that was lost, what the other side did, how you know it, and the damages you can trace. We also consider whether a direct letter or an injunction request would serve you more than a damages case, since the business goal is often to stop the conduct quickly.
